WEBVTT 00:00:00.000 --> 00:00:02.560 Imagine you're swimming in a massive, crowded, 00:00:02.660 --> 00:00:05.299 underwater neighborhood. But this is definitely 00:00:05.299 --> 00:00:08.000 not a vibrant little coral reef filled with colorful 00:00:08.000 --> 00:00:11.199 fish darting around anemones. Right, no. You 00:00:11.199 --> 00:00:13.980 are swimming through a Jurassic Sea. And every 00:00:13.980 --> 00:00:16.920 single shadow passing over you belongs to an 00:00:16.920 --> 00:00:20.589 apex predator. It's a prehistoric ecosystem packed 00:00:20.589 --> 00:00:23.850 to the absolute brim, just overflowing with marine 00:00:23.850 --> 00:00:26.629 reptiles, heavily armored fish, and these deep 00:00:26.629 --> 00:00:28.829 diving ichthyosaurs. It's terrifying to even 00:00:28.829 --> 00:00:32.189 picture. And today we are going to focus on one 00:00:32.189 --> 00:00:35.149 very particular creature from this ancient ocean, 00:00:35.350 --> 00:00:38.670 a creature that, well, scientists have been arguing 00:00:38.670 --> 00:00:42.009 about for over 150 years. Yeah, it genuinely 00:00:42.009 --> 00:00:44.210 stands as one of the most frustrating and honestly 00:00:44.210 --> 00:00:47.530 fascinating taxonomic puzzles in all of paleontology. 00:00:47.560 --> 00:00:50.179 Because the animal we're examining today has 00:00:50.179 --> 00:00:53.780 been named, renamed, categorized, and then aggressively 00:00:53.780 --> 00:00:56.579 evicted from its own family tree more times than 00:00:56.579 --> 00:00:58.939 almost any other marine reptile. It really is 00:00:58.939 --> 00:01:00.859 the perfect case study. It shows exactly how 00:01:00.859 --> 00:01:03.159 difficult it is to categorize ancient life when 00:01:03.159 --> 00:01:05.060 all you have are scattered fragments of bone 00:01:05.060 --> 00:01:07.939 and a constantly shifting understanding of evolution. 00:01:08.489 --> 00:01:11.049 Which brings us to today's source material. We're 00:01:11.049 --> 00:01:13.810 pulling from a comprehensive Wikipedia article 00:01:13.810 --> 00:01:17.030 detailing the extinct marine reptile currently 00:01:17.030 --> 00:01:20.689 known as Pleiosaurus andrusi. Or at least that's 00:01:20.689 --> 00:01:23.269 what we call it for now. Right. So our mission 00:01:23.269 --> 00:01:26.769 for this deep dive is threefold. First, we're 00:01:26.769 --> 00:01:28.950 going to explore the century and a half long 00:01:28.950 --> 00:01:32.269 soap opera of how this animal was actually classified. 00:01:32.609 --> 00:01:34.790 The drama is real with this one. It really is. 00:01:35.159 --> 00:01:37.439 Second, we're going to reconstruct this unique 00:01:37.439 --> 00:01:40.200 apex predator from snout to flipper, looking 00:01:40.200 --> 00:01:42.840 at a physical contradiction that completely baffled 00:01:42.840 --> 00:01:45.099 scientists. A very weird contradiction, yes. 00:01:45.260 --> 00:01:47.019 And third, we are going to figure out exactly 00:01:47.019 --> 00:01:49.780 how it managed to survive in a sea completely 00:01:49.780 --> 00:01:53.310 overloaded with rival sea monsters. Okay, let's 00:01:53.310 --> 00:01:55.689 unpack this. Starting with an identity crisis 00:01:55.689 --> 00:01:58.810 that spans generations of paleontologists. Calling 00:01:58.810 --> 00:02:01.269 it an identity crisis might actually be underselling 00:02:01.269 --> 00:02:03.930 it. The timeline of discovering and naming this 00:02:03.930 --> 00:02:06.390 animal is incredibly convoluted. Let's wind the 00:02:06.390 --> 00:02:08.909 clock all the way back to 1871. We have a scientist 00:02:08.909 --> 00:02:11.050 named John Phillips. Right, and he's examining 00:02:11.050 --> 00:02:13.189 some plasaur fossils that were found by Charles 00:02:13.189 --> 00:02:15.629 Leeds over in England. Specifically in the Oxford 00:02:15.629 --> 00:02:18.310 Clay Formation, yeah. So Phillips is looking 00:02:18.310 --> 00:02:21.400 at a swimming paddle. And a pretty well -preserved 00:02:21.400 --> 00:02:24.379 jawbone. And he analyzes these pieces and he 00:02:24.379 --> 00:02:28.520 decides to name the creature Pleiosaurus, question 00:02:28.520 --> 00:02:31.240 mark, Grandus. He literally includes a question 00:02:31.240 --> 00:02:33.860 mark in the official scientific name. He does. 00:02:33.979 --> 00:02:36.120 I mean, that feels like the 19th century equivalent 00:02:36.120 --> 00:02:38.280 of a paleontologist just throwing their hands 00:02:38.280 --> 00:02:40.120 up in the air and saying, I have no idea. It 00:02:40.120 --> 00:02:42.860 really is. But it's also a remarkable bit of 00:02:42.860 --> 00:02:45.830 honesty for that era. Because that question mark 00:02:45.830 --> 00:02:48.689 tells you immediately that Felix wasn't entirely 00:02:48.689 --> 00:02:51.430 convinced by his own classification. He knew 00:02:51.430 --> 00:02:53.610 he had a large marine reptile, but the proportions 00:02:53.610 --> 00:02:56.669 just didn't fit, right? Exactly. The morphology 00:02:56.669 --> 00:02:59.009 of that jawbone didn't neatly align with the 00:02:59.009 --> 00:03:01.370 existing understanding of the Pleiosaurus genus 00:03:01.370 --> 00:03:04.629 at the time. And that initial hesitation, well, 00:03:04.729 --> 00:03:06.629 it basically opened the floodgates for decades 00:03:06.629 --> 00:03:09.650 of taxonomic chaos. Total chaos. Because jump 00:03:09.650 --> 00:03:13.129 to 1889 and another paleontologist, Richard Lidecker, 00:03:13.250 --> 00:03:15.509 steps up to the plate. Lidecker takes one look 00:03:15.509 --> 00:03:17.870 at the specimen and decides Phillips was completely 00:03:17.870 --> 00:03:21.110 wrong. Right. He moves the animal into a totally 00:03:21.110 --> 00:03:24.210 different genus. He renames it Planastes phylarchus. 00:03:25.229 --> 00:03:27.349 But he doesn't even stick to his own theory. 00:03:27.629 --> 00:03:30.250 No, he doesn't. Just one year later in 1890, 00:03:30.550 --> 00:03:32.370 he changes his mind again. Just because he notices 00:03:32.370 --> 00:03:35.150 these bones are significantly larger than other 00:03:35.150 --> 00:03:38.270 typical Pleinastes specimens. Right, so he reassigns 00:03:38.270 --> 00:03:42.009 it yet again to a proposed species called Pleinastes 00:03:42.009 --> 00:03:45.069 avansi. This sounds exhausting. A classic problem 00:03:45.069 --> 00:03:47.930 in early paleontology, honestly. Size was very 00:03:47.930 --> 00:03:50.509 often used as a primary metric for determining 00:03:50.509 --> 00:03:52.969 a new species. Instead of looking at the actual 00:03:52.969 --> 00:03:56.060 nuanced anatomical differences. Exactly. Lidecker 00:03:56.060 --> 00:03:58.319 saw a bigger bone and just assumed, well, it 00:03:58.319 --> 00:04:00.639 has to be a different species within the Polonistes 00:04:00.639 --> 00:04:04.080 umbrella. And so the animal just sat there, categorized 00:04:04.080 --> 00:04:07.240 under that name, gathering dust until 1913. Which 00:04:07.240 --> 00:04:09.159 is when Charles William Andrews enters the narrative. 00:04:09.319 --> 00:04:11.740 Right. Andrews examines a partial skeleton of 00:04:11.740 --> 00:04:14.539 a large pliosaur found by Leeds, and he starts 00:04:14.539 --> 00:04:16.720 to notice fundamental structural differences. 00:04:17.160 --> 00:04:19.579 He realizes that the jaw and the vertebrae are 00:04:19.579 --> 00:04:22.060 morphologically completely distinct from Polonistes. 00:04:22.480 --> 00:04:24.740 He essentially looks at it and says, this isn't 00:04:24.740 --> 00:04:27.339 Pellenestes and it isn't quite Pliosaurus. It's 00:04:27.339 --> 00:04:30.839 doing its own thing. He recognizes it as an intermediate 00:04:30.839 --> 00:04:34.040 form, a bridge between species. But amazingly, 00:04:34.379 --> 00:04:37.180 it takes almost another 50 years for anyone to 00:04:37.180 --> 00:04:39.740 formally act on Andrew's observation. Science 00:04:39.740 --> 00:04:42.490 can move. Very slowly sometimes. Yeah. Fast forward 00:04:42.490 --> 00:04:45.750 to 1960. A scientist named Lambert Beverly Tarlow 00:04:45.750 --> 00:04:48.069 decides to finally clean up the mess. Tarlow 00:04:48.069 --> 00:04:50.810 selects a very specific partial skeleton, one 00:04:50.810 --> 00:04:53.410 that features a complete spine, the jaw, and 00:04:53.410 --> 00:04:55.689 the limbs. And he designates that as the holotype, 00:04:55.870 --> 00:04:58.069 the gold standard for the species. Right. And 00:04:58.069 --> 00:05:00.569 he officially names the creature Pleiosaurus 00:05:00.569 --> 00:05:04.680 andrugosae. He uses that specific epithet to 00:05:04.680 --> 00:05:07.379 directly honor Charles William Andrews for his 00:05:07.379 --> 00:05:10.459 insights way back in 1913. And at that point, 00:05:10.480 --> 00:05:12.040 you would think the debate was finally closed, 00:05:12.220 --> 00:05:14.800 right? You really would. Tarlow established a 00:05:14.800 --> 00:05:17.060 holotype, honored the scientist who recognized 00:05:17.060 --> 00:05:19.939 its unique traits, and firmly planted it in the 00:05:19.939 --> 00:05:22.939 pliosaurus genus. For decades, this classification 00:05:22.939 --> 00:05:25.660 was considered entirely settled. But taxonomy 00:05:25.660 --> 00:05:28.019 is never truly finished. No, it simply waits 00:05:28.019 --> 00:05:30.459 for better analytical tools. Which brings us 00:05:30.459 --> 00:05:34.250 to the 2010s. when modern science drops a massive 00:05:34.250 --> 00:05:36.550 plot twist on this poor creature's identity. 00:05:37.029 --> 00:05:39.870 After fighting for a century to get this animal 00:05:39.870 --> 00:05:42.550 properly classified into the Pleiosaurus genus, 00:05:42.589 --> 00:05:45.350 a new wave of researchers ended up kicking it 00:05:45.350 --> 00:05:47.389 right back out. They did. What's fascinating 00:05:47.389 --> 00:05:50.149 here is how the advent of modern computational 00:05:50.149 --> 00:05:53.750 biology completely upended a century of visual 00:05:53.750 --> 00:05:55.910 assumptions. What's fascinating here is exactly 00:05:55.910 --> 00:05:59.379 that. In the early 2010s, Researchers conducted 00:05:59.379 --> 00:06:02.600 rigorous phylogenetic and anatomical revisions. 00:06:02.860 --> 00:06:05.519 They took all the morphological data, every ridge 00:06:05.519 --> 00:06:07.459 on the teeth, every measurement of the vertebrae, 00:06:07.459 --> 00:06:10.100 the exact proportions of the skull, and fed it 00:06:10.100 --> 00:06:12.500 into modern cladistic analyses. So they let the 00:06:12.500 --> 00:06:14.639 computers do the heavy lifting. Right. And the 00:06:14.639 --> 00:06:17.569 resulting family tree was undeniable. This animal 00:06:17.569 --> 00:06:19.709 possessed unique characteristics, particularly 00:06:19.709 --> 00:06:22.490 in its teeth, that separated it from every valid 00:06:22.490 --> 00:06:24.829 species of Pliosaurus. It's incredible. The computer 00:06:24.829 --> 00:06:26.750 essentially looked at the data and confirmed 00:06:26.750 --> 00:06:29.509 what John Phillips suspected in 1871 with his 00:06:29.509 --> 00:06:32.209 little question mark. Full circle. Yeah. And 00:06:32.209 --> 00:06:34.310 because it doesn't belong in Pliosaurus, but 00:06:34.310 --> 00:06:36.449 hasn't officially been assigned a new genus name 00:06:36.449 --> 00:06:39.290 yet, the scientific community handles this in 00:06:39.290 --> 00:06:42.550 a wonderfully quirky way. Today, its name is 00:06:42.550 --> 00:06:45.490 written as Pleiosaurus in quotation marks, followed 00:06:45.490 --> 00:06:48.430 by Andrusi. It wears those quotation marks like 00:06:48.430 --> 00:06:51.490 a temporary badge, just signifying its pending 00:06:51.490 --> 00:06:54.129 taxonomic status. It's like calling it the artist 00:06:54.129 --> 00:06:56.670 formerly known as Pleiosaurus. So where does 00:06:56.670 --> 00:06:59.129 it actually belong? Well, the current consensus 00:06:59.129 --> 00:07:02.610 places Pleiosaurus Andrusi as a basal member 00:07:02.610 --> 00:07:05.889 of a clade called Thalassophonia. Okay, let's 00:07:05.889 --> 00:07:08.180 break that down for the listeners. Sure. Phallosophonia 00:07:08.180 --> 00:07:11.060 is a specific group of short -necked pliosaurs. 00:07:11.279 --> 00:07:14.139 And being a basal member means it sits near the 00:07:14.139 --> 00:07:16.399 root of that family tree. It's somewhere right 00:07:16.399 --> 00:07:18.740 between Poliniastes and Simulastes. So it's a 00:07:18.740 --> 00:07:21.329 transitional form. Exactly. Being a transitional 00:07:21.329 --> 00:07:24.069 form like this makes its anatomy incredibly revealing 00:07:24.069 --> 00:07:26.610 because it bridges the evolutionary gap between 00:07:26.610 --> 00:07:29.269 completely different types of specialized marine 00:07:29.269 --> 00:07:31.569 hunters. Let's actually build this beast for 00:07:31.569 --> 00:07:33.829 you, the listener, because the anatomy is where 00:07:33.829 --> 00:07:36.250 this story shifts from a historical puzzle into 00:07:36.250 --> 00:07:39.050 a true biological marvel. Paint the picture. 00:07:39.230 --> 00:07:41.610 If this animal swam past you in that Jurassic 00:07:41.610 --> 00:07:44.790 Sea, it would present a classic pleosauromorph 00:07:44.790 --> 00:07:48.889 body plan. It was a medium -sized marine reptile. 00:07:49.230 --> 00:07:52.189 But keep in mind, medium in this ecosystem means 00:07:52.189 --> 00:07:54.769 it had a skull that measured one full meter in 00:07:54.769 --> 00:07:57.670 length. It's over three feet of pure jaw and 00:07:57.670 --> 00:08:00.620 muscle, just the head. Right. Behind that massive 00:08:00.620 --> 00:08:03.060 skull, it had a heavily built barrel -shaped 00:08:03.060 --> 00:08:05.699 body. Which was designed for powerful bursts 00:08:05.699 --> 00:08:08.220 of speed rather than sustained graceful cruising. 00:08:08.379 --> 00:08:10.920 And it had a remarkably short neck, like exactly 00:08:10.920 --> 00:08:15.160 78 .3 centimeters long, based on a 2023 study 00:08:15.160 --> 00:08:17.560 of the Holotech specimen. They get incredibly 00:08:17.560 --> 00:08:20.120 precise with these measurements. And to navigate 00:08:20.120 --> 00:08:23.430 the water, it utilized four large flippers. But 00:08:23.430 --> 00:08:25.250 the back pair were larger, right? Yeah, the hind 00:08:25.250 --> 00:08:27.709 flippers were noticeably larger and more robust 00:08:27.709 --> 00:08:30.089 than the front ones, which provided the primary 00:08:30.089 --> 00:08:32.429 thrust for swimming. But the defining feature 00:08:32.429 --> 00:08:34.470 of this animal, the thing that caused so much 00:08:34.470 --> 00:08:37.169 confusion, is what was going on inside that one 00:08:37.169 --> 00:08:40.289 meter skull. The teeth. At the very front of 00:08:40.289 --> 00:08:42.929 the jaw were the two halves, meet the symphysis 00:08:42.929 --> 00:08:45.690 it had up to 12 pairs of teeth. And the seventh 00:08:45.690 --> 00:08:49.470 pair were these massive, deeply rooted, canine 00:08:49.470 --> 00:08:52.470 -like teeth. Operating with about 64 teeth in 00:08:52.470 --> 00:08:54.710 total. And the structure of those teeth is the 00:08:54.710 --> 00:08:57.509 absolute key to unlocking its ecological role. 00:08:57.710 --> 00:09:00.269 They are highly distinct. In cross -section, 00:09:00.450 --> 00:09:02.870 they're completely round. and they feature these 00:09:02.870 --> 00:09:06.110 subtle longitudinal ridges running down the crown. 00:09:06.289 --> 00:09:08.830 But that's not the weirdest part. No. The critical 00:09:08.830 --> 00:09:10.809 detail of the anomaly that separates it from 00:09:10.809 --> 00:09:13.610 its close relatives is the wear and tear. The 00:09:13.610 --> 00:09:16.470 dental crowns exhibit a level of extreme abrasion. 00:09:16.549 --> 00:09:19.309 It extends considerably further down the tooth 00:09:19.309 --> 00:09:22.299 than in any other known plesiosaur. This is the 00:09:22.299 --> 00:09:24.700 grand contradiction of Pleisosaurus and Druzy. 00:09:24.799 --> 00:09:26.700 If you look at the shape of its skull, it has 00:09:26.700 --> 00:09:30.019 an elongated, narrow snout. Which, evolutionarily 00:09:30.019 --> 00:09:32.720 speaking, is almost universally adapted for catching 00:09:32.720 --> 00:09:35.179 small, agile, slippery fish. Right. A narrow 00:09:35.179 --> 00:09:37.960 snout lets a predator snap its jaws shut through 00:09:37.960 --> 00:09:39.960 the water quickly because there's minimal drag. 00:09:40.259 --> 00:09:42.080 But its teeth tell a totally different story. 00:09:42.640 --> 00:09:45.120 Exactly. Its teeth were perfectly suited for 00:09:45.120 --> 00:09:47.799 heavy -duty cutting, and they were heavily worn 00:09:47.799 --> 00:09:49.919 down. If we connect this to the bigger picture 00:09:49.919 --> 00:09:52.960 for a second, you do not get extreme dental abrasion 00:09:52.960 --> 00:09:55.559 and deep wear patterns on cutting teeth from 00:09:55.559 --> 00:09:58.360 eating soft -bodied fish. You just don't. That 00:09:58.360 --> 00:10:01.860 specific type of wear strongly indicates it was 00:10:01.860 --> 00:10:04.759 attacking much larger, highly resistant prey. 00:10:05.200 --> 00:10:08.279 It's an incredible morphological paradox. It 00:10:08.279 --> 00:10:10.799 possessed the quick -snapping, low -drag jaw 00:10:10.799 --> 00:10:13.659 of a fish eater combined with the heavy -duty, 00:10:13.679 --> 00:10:16.679 heavily -worn dentition of an apex big game hunter. 00:10:16.879 --> 00:10:19.399 It completely broke the standard ecological rules 00:10:19.399 --> 00:10:21.879 regarding what long -snouted predators are actually 00:10:21.879 --> 00:10:24.600 supposed to hunt. So to understand why it evolved 00:10:24.600 --> 00:10:27.279 this specific contradiction, we need to look 00:10:27.279 --> 00:10:29.240 at exactly where it lived. We are traveling back 00:10:29.240 --> 00:10:31.279 to the Kolovian stage of the Middle Jurassic. 00:10:31.679 --> 00:10:35.759 Spanning roughly 166 to 164 million years ago. 00:10:36.059 --> 00:10:38.340 Geographically, we are focusing on the Peterborough 00:10:38.340 --> 00:10:41.220 member of the Oxford Clay Formation in modern 00:10:41.220 --> 00:10:44.019 -day England. Though the geography of the Calovian 00:10:44.019 --> 00:10:46.440 stage was vastly different from today. Right, 00:10:46.480 --> 00:10:48.419 the landmass that would eventually become England 00:10:48.419 --> 00:10:50.820 was submerged beneath an epicontinental sea. 00:10:50.960 --> 00:10:54.059 A shallow inland sea, situated at a latitude 00:10:54.059 --> 00:10:56.669 of roughly 35 degrees north. And when we say 00:10:56.669 --> 00:10:58.850 shallow, we really mean it. A depth of only about 00:10:58.850 --> 00:11:02.250 30 to 50 meters. That's incredibly shallow for 00:11:02.250 --> 00:11:04.990 a sea packed with giant monsters. It is. But 00:11:04.990 --> 00:11:07.789 up in the surrounding land masses, the environment 00:11:07.789 --> 00:11:10.590 was surprisingly pleasant. It featured a Mediterranean 00:11:10.590 --> 00:11:13.590 climate with dry summers and wet winters. Though 00:11:13.590 --> 00:11:15.629 the region was gradually shifting toward a more 00:11:15.629 --> 00:11:18.789 arid climate. But the water itself was temperate. 00:11:19.200 --> 00:11:22.240 Isotope analysis from fossilized bivalves shows 00:11:22.240 --> 00:11:24.379 that the water temperature averaged around 15 00:11:24.379 --> 00:11:27.299 degrees Celsius. Or 59 degrees Fahrenheit. Right. 00:11:27.399 --> 00:11:29.820 And it fluctuated seasonally, dropping to about 00:11:29.820 --> 00:11:31.799 11 degrees Celsius in the winter and warming 00:11:31.799 --> 00:11:34.419 up to 17 degrees in the summer. But the chemical 00:11:34.419 --> 00:11:37.159 composition of that 50 meter deep water column 00:11:37.159 --> 00:11:40.100 was highly unusual. The sediment reveals the 00:11:40.100 --> 00:11:42.559 presence of green sulfur bacteria. And what does 00:11:42.559 --> 00:11:44.519 that tell us? Well, in modern marine environments, 00:11:44.909 --> 00:11:47.350 Green sulfur bacteria are a clear indicator of 00:11:47.350 --> 00:11:51.049 eucinic conditions. Meaning low oxygen. Severely 00:11:51.049 --> 00:11:53.970 depleted oxygen levels, yes. Paired with high 00:11:53.970 --> 00:11:57.850 concentrations of toxic hydrogen sulfide. Typically, 00:11:57.970 --> 00:12:00.750 those chemical markers suggest a stagnant dead 00:12:00.750 --> 00:12:03.710 zone where complex life just cannot survive. 00:12:04.009 --> 00:12:05.909 But the Peterborough member was the furthest 00:12:05.909 --> 00:12:08.899 thing from a dead zone. The fossil record is 00:12:08.899 --> 00:12:11.299 packed with abundant traces of benthic organisms, 00:12:11.519 --> 00:12:14.100 creatures thriving right down on the seafloor. 00:12:14.220 --> 00:12:16.259 Which tells us that while there were definitely 00:12:16.259 --> 00:12:18.980 eucenic elements to the water chemistry, the 00:12:18.980 --> 00:12:21.240 bottom waters were not completely or permanently 00:12:21.240 --> 00:12:24.580 anoxic. The oxygen levels were dynamic. Here's 00:12:24.580 --> 00:12:27.000 where it gets really interesting. Because the 00:12:27.000 --> 00:12:29.519 sheer volume and diversity of life sharing this 00:12:29.519 --> 00:12:32.639 specific body of water is just staggering. Oh, 00:12:32.659 --> 00:12:34.940 it was packed. If you were diving in this 50 00:12:34.940 --> 00:12:37.240 meter deep epicontinental sea, you... You'd be 00:12:37.240 --> 00:12:40.159 surrounded by vast swarms of invertebrates, shelled 00:12:40.159 --> 00:12:42.759 ammonites, belemnites. You'd see a massive variety 00:12:42.759 --> 00:12:45.700 of fish, too, ranging from small, agile swimmers 00:12:45.700 --> 00:12:47.960 all the way up to lead sickness. Right, that 00:12:47.960 --> 00:12:50.519 colossal, filter -feeding fish that cruise through 00:12:50.519 --> 00:12:53.000 the water like a Jurassic baleen whale. You would 00:12:53.000 --> 00:12:55.879 also encounter smaller, long -necked plesiosaurs 00:12:55.879 --> 00:12:58.980 like Cryptoclytus, specializing in darting its 00:12:58.980 --> 00:13:01.620 head around to snatch up small prey. And don't 00:13:01.620 --> 00:13:04.360 forget Ophthalmosaurus, that highly specialized 00:13:04.360 --> 00:13:07.399 ichthyosaur with a porcus -like... body and gigantic 00:13:07.399 --> 00:13:10.779 eyes, perfectly adapted for diving into the darker 00:13:10.779 --> 00:13:14.419 depths to hunt squid. Add to that multiple genera 00:13:14.419 --> 00:13:17.460 of marine crocodilians, some sleek and adapted 00:13:17.460 --> 00:13:20.149 for fish catching, others heavily armored. But 00:13:20.149 --> 00:13:22.629 the invertebrates, the giant fish, the marine 00:13:22.629 --> 00:13:25.269 crocs, they weren't the real issue in this ecosystem. 00:13:25.570 --> 00:13:28.389 The primary overcrowding problem came from the 00:13:28.389 --> 00:13:31.490 pliosaurids. The apex predators. Right. The fossil 00:13:31.490 --> 00:13:33.210 assemblage at the Peterborough member contains 00:13:33.210 --> 00:13:35.990 more species of pliosaurids than any other known 00:13:35.990 --> 00:13:38.049 site on Earth. This raises an important question. 00:13:38.350 --> 00:13:40.970 How do you fit that many distinct apex predators 00:13:40.970 --> 00:13:44.049 into a single shallow inland sea without them 00:13:44.049 --> 00:13:46.750 completely devastating the food web or just fiercely 00:13:46.750 --> 00:13:49.029 out -competing each other into extinction? Let's 00:13:49.029 --> 00:13:50.539 look at the... absolute gauntlet of neighbors 00:13:50.539 --> 00:13:52.860 that our animal, Pliosaurus and Drusae, had to 00:13:52.860 --> 00:13:55.620 deal with. You have Leopleurodon, Similostes, 00:13:55.679 --> 00:13:59.980 Poloniestes, Marmonectes, Vertosaurus, and Pachycostosaurus. 00:14:00.340 --> 00:14:03.799 That is at least seven different massive, heavily 00:14:03.799 --> 00:14:07.480 armed, carnivorous marine reptiles occupying 00:14:07.480 --> 00:14:10.620 the exact same 50 meters of water. It sounds 00:14:10.620 --> 00:14:12.879 like a recipe for starvation. How did they do 00:14:12.879 --> 00:14:15.179 it? The mechanism that allowed them to coexist? 00:14:16.000 --> 00:14:19.039 is a biological concept known as niche partitioning. 00:14:19.080 --> 00:14:21.500 Meaning they divided up the resources. Exactly. 00:14:21.720 --> 00:14:24.919 In highly crowded ecosystems, evolutionary pressure 00:14:24.919 --> 00:14:27.840 forces predators to specialize incredibly thoroughly. 00:14:28.100 --> 00:14:31.139 They divide the available resources so precisely 00:14:31.139 --> 00:14:34.320 that direct competition is minimized. They essentially 00:14:34.320 --> 00:14:36.440 split up the buffet menu. That's a great way 00:14:36.440 --> 00:14:38.320 to put it. And the Peterborough member stands 00:14:38.320 --> 00:14:41.480 as a master class in how nature engineers this 00:14:41.480 --> 00:14:43.990 delicate balance. Let's walk through that divided 00:14:43.990 --> 00:14:46.809 buffet. First, you have Liopleurodon and Erdosaurus. 00:14:46.970 --> 00:14:49.029 Right. These were the absolute heavy hitters 00:14:49.029 --> 00:14:51.990 of the ecosystem. They possessed massive, structurally 00:14:51.990 --> 00:14:54.809 robust skulls and powerful cutting teeth. So 00:14:54.809 --> 00:14:56.889 they claimed the top of the food chain. They 00:14:56.889 --> 00:14:58.909 did. They specialized in hunting the largest 00:14:58.909 --> 00:15:01.149 prey available, which likely meant preying on 00:15:01.149 --> 00:15:03.730 other large marine reptiles and the biggest fish. 00:15:04.080 --> 00:15:06.820 Then you have semolestes, which took a completely 00:15:06.820 --> 00:15:09.440 different morphological approach. It featured 00:15:09.440 --> 00:15:12.720 a very wide, exceptionally deep skull that housed 00:15:12.720 --> 00:15:15.919 a tremendously powerful bite force. Its specific 00:15:15.919 --> 00:15:18.659 niche was likely crushing large, tough -shelled 00:15:18.659 --> 00:15:21.899 cephalopods. It didn't need a streamlined snout 00:15:21.899 --> 00:15:25.100 to chase fast fish. It simply needed the raw 00:15:25.100 --> 00:15:28.100 mechanical jaw strength to shatter heavy armor. 00:15:28.440 --> 00:15:30.120 On the opposite end of the spectrum, you have 00:15:30.120 --> 00:15:32.799 the fast fish hunters. That nooch was dominated 00:15:32.799 --> 00:15:36.179 by palenonastes. Right. It evolved a highly elongated 00:15:36.179 --> 00:15:39.299 snout and sharp, piercing teeth, making it perfectly 00:15:39.299 --> 00:15:42.480 adapted for snapping up small, highly agile prey 00:15:42.480 --> 00:15:45.419 with minimal water resistance. We also have to 00:15:45.419 --> 00:15:47.759 mention Pachycustasaurus, which found an entirely 00:15:47.759 --> 00:15:50.139 different way to avoid competition. It was a 00:15:50.139 --> 00:15:52.519 smaller, exceptionally heavily built pliosaur. 00:15:52.860 --> 00:15:55.019 Its skeletal structure was incredibly dense, 00:15:55.120 --> 00:15:57.139 and its skull was structurally weaker than the 00:15:57.139 --> 00:15:59.600 midwater hunters. So it stayed low. Exactly. 00:15:59.740 --> 00:16:02.700 That immense bone density made it highly stable, 00:16:02.860 --> 00:16:04.960 strongly suggesting it was a dedicated bottom 00:16:04.960 --> 00:16:07.779 feeder. It cruised along the seafloor, picking 00:16:07.779 --> 00:16:10.179 up benthic prey, keeping completely out of the 00:16:10.179 --> 00:16:12.019 way of the massive predators hunting above it. 00:16:12.320 --> 00:16:15.240 Which brings us back to Pliosaurus indrusi navigating 00:16:15.240 --> 00:16:18.940 this incredibly specific ecosystem with its cortation 00:16:18.940 --> 00:16:21.940 marks and its contradictory anatomy. Right, because 00:16:21.940 --> 00:16:24.279 it was physically larger than the fish -eating 00:16:24.279 --> 00:16:27.360 Polonastes, and it shared that same low -drag, 00:16:27.360 --> 00:16:30.559 elongated snout. But it also possessed those 00:16:30.559 --> 00:16:33.080 uniquely worn -down, heavily abraded, cutting 00:16:33.080 --> 00:16:35.659 teeth. Through niche partitioning, Pliosaurus 00:16:35.659 --> 00:16:38.139 and Druzy carved out its own highly specific 00:16:38.139 --> 00:16:40.940 menu item. It utilized its quick -snapping jaws 00:16:40.940 --> 00:16:43.539 to capture prey that was larger and tougher than 00:16:43.539 --> 00:16:45.340 the other long -snatted predators could handle, 00:16:45.460 --> 00:16:48.000 relying on its specialized cutting teeth to slice 00:16:48.000 --> 00:16:50.440 through them. Every single one of these massive 00:16:50.440 --> 00:16:53.919 marine reptiles survived by becoming a hyperspecialist. 00:16:53.960 --> 00:16:55.899 They subtly treat the length of their snouts, 00:16:56.019 --> 00:16:58.059 the exact cross -section of their teeth, and 00:16:58.059 --> 00:17:00.399 the density of their skeletal structure, just 00:17:00.399 --> 00:17:03.139 enough to claim a unique, undisputed slice of 00:17:03.139 --> 00:17:05.480 the ecosystem. It is a stunning demonstration 00:17:05.480 --> 00:17:08.700 of evolutionary adaptation thriving within a 00:17:08.700 --> 00:17:11.119 confined environment. It really is. So what does 00:17:11.119 --> 00:17:13.420 this all mean? We started this deep dive looking 00:17:13.420 --> 00:17:16.500 at a confusing collection of bones that had paleontologists 00:17:16.500 --> 00:17:20.000 second -guessing themselves from 1871 well into 00:17:20.000 --> 00:17:23.079 the 2010s. And we uncover two brilliant takeaways. 00:17:23.440 --> 00:17:26.220 First, we see that science is a living, continuously 00:17:26.220 --> 00:17:29.559 self -correcting process. The quotation marks 00:17:29.559 --> 00:17:32.259 around Pliosaurus aren't a failure of taxonomy. 00:17:32.480 --> 00:17:34.859 They're a testament to the rigorous, ongoing 00:17:34.859 --> 00:17:37.779 revision of our understanding as new data and 00:17:37.779 --> 00:17:40.880 cladistic tools emerge. Absolutely. And second, 00:17:41.019 --> 00:17:44.049 we wit - the sheer brilliance of niche partitioning. 00:17:44.190 --> 00:17:46.869 Life in the Oxford Clay Formation didn't just 00:17:46.869 --> 00:17:50.089 fiercely compete for a single resource. It adapted, 00:17:50.289 --> 00:17:52.890 partitioned, and specialized, allowing an incredibly 00:17:52.890 --> 00:17:56.029 diverse community of apex predators to thrive 00:17:56.029 --> 00:17:58.789 together in a shallow, fluctuating sea. There 00:17:58.789 --> 00:18:01.190 is, however, an inevitable consequence to that 00:18:01.190 --> 00:18:03.450 level of brilliant specialization. What do you 00:18:03.450 --> 00:18:06.170 mean? Well, the fossil record reveals that these 00:18:06.170 --> 00:18:09.049 long -snouted, passivorous forms like Pliosaurus 00:18:09.049 --> 00:18:11.890 and Drusii completely died out at the boundary 00:18:11.890 --> 00:18:14.130 between the middle and upper Jurassic. Oh, wow. 00:18:14.309 --> 00:18:16.890 Yeah. This specific extinction event kicked off 00:18:16.890 --> 00:18:19.769 a gradual widespread decline in all plesiosaur 00:18:19.769 --> 00:18:22.910 diversity. And it wasn't caused by a sudden catastrophic 00:18:22.910 --> 00:18:26.170 asteroid impact. It was driven by shifting ocean 00:18:26.170 --> 00:18:28.930 chemistry and steadily falling sea levels. So 00:18:28.930 --> 00:18:30.950 the environment just slowly changed around them. 00:18:31.130 --> 00:18:34.920 Exactly. An ecosystem becomes as perfectly partitioned 00:18:34.920 --> 00:18:37.680 and tightly specialized as the Oxford Clay Sea, 00:18:37.880 --> 00:18:40.700 where every animal has evolved a highly specific 00:18:40.700 --> 00:18:44.240 jaw to consume a highly specific prey item. That 00:18:44.240 --> 00:18:46.400 very perfection makes them incredibly fragile. 00:18:46.579 --> 00:18:49.039 Because they have no backup plan. Right. When 00:18:49.039 --> 00:18:50.799 the ocean chemistry shifts and the water levels 00:18:50.799 --> 00:18:54.829 drop, the available buffet menu changes. Teeth, 00:18:54.849 --> 00:18:57.609 your jaw, and your entire body plan are irreversibly 00:18:57.609 --> 00:18:59.950 designed to eat only one thing. You are left 00:18:59.950 --> 00:19:02.190 entirely without options when that one thing 00:19:02.190 --> 00:19:04.809 disappears. That is a fascinating and sobering 00:19:04.809 --> 00:19:06.710 thought to leave on. Thank you for joining us 00:19:06.710 --> 00:19:09.450 on this deep dive into the chaotic taxonomic 00:19:09.450 --> 00:19:11.990 history, the bizarre anatomy, and the densely 00:19:11.990 --> 00:19:14.950 packed world of Pliosaurus and Drusorsi. Keep 00:19:14.950 --> 00:19:16.769 digging into the mysteries of the ancient world, 00:19:16.809 --> 00:19:18.470 and we will catch you on the next one.